Photoflash lamp having non-shorting construction

ABSTRACT

A glass sleeve is positioned around one inlead of a photoflash lamp, so that the second inlead is bare for a greater distance from the filament (or other ignition means) than is the sleeved inlead. When the lamp is flashed, the unsleeved inlead burns back farther than the sleeved inlead, thus causing a relatively large electrical path between the exposed parts of the burned-back inleads and reducing the likelihood of them becoming shorted either directly together or by metal fragments in the flashed lamp.

United States Patent Baldrige, Jr. et al.

[4 1 June 11, 1974 PHOTOFLASH LAMP HAVING NON-SHORTING CONSTRUCTION [75] Inventors: John Baldrige, Jr., Chesterland;

John C. Sobieski, Russell Twp., both of Ohio [73] Assignee: General Electric Company,

Schenectady, NY.

22 Filed: May 2,1973

21 Appl. No.: 356,459

[52] US. Cl. 431/95 [51] Int. Cl. F2lk 5/02 [58] Field of Search 431/93-95 .[56] References Cited UNITED STATES PATENTS 2/1937 Williams et al. 431/95 3,556,699 l/l97l Takahashi et al 431/95 Primary Examiner-Carroll B. Dority, Jr. Attorney, Agent, or FirmNorman C. Fulmer; Lawrence R. Kempton; Frank L. Neuhauser [5 7 ABSTRACT A glass sleeve is positioned around one inlead of a photoflash lamp, so that the second inlead is bare for a greater distance from the filament (or other ignition means) than is the sleeved inlead. When the lamp is flashed, the unsleeved inlead burns back farther than the sleeved inlead, thus causing a relatively large electrical path between the exposed parts of the burnedback inleads and reducing the likelihood of them becoming shorted either directly together or by metal fragments in the flashed lamp.

12 Claims, 4 Drawing Figures PHOTOFLASII LAMP HAVING NON-SHORTING CONSTRUCTION BACKGROUND OF THE INVENTION The invention is in the fluid of photoflash lamps of the type in which a pair of inleads carry a filamentor other electrical ignition means inside a bulb containing combustible material such as shredded metal foil and a combustionsupporting gas such as oxygen.

When such a photoflash lamp is flashed, the shredded metal foil burns in an oxygen atmosphere and produces an intense flash of light, accompanied by intense heat which burns back the inleads. Occasionally some remnants of metal will remain in a flashed lamp and tend to bridge across the burned-back inleads, causing an electrically shorted flashed lamp. Also, the burnedback inleads sometimes become distorted and/or melt and fuse together, causing a directly contacting short with one another. This shorting is undesirable because it will cause a short circuit on the battery or other power source until the lamp is removed from the circuit. Many lamp flashing circuits alleviate the problem by providing a quick make-and-break synchronizing switch which, after closing to apply current to the filament to causea lamp to flash, immediately opens to provide an afterflash open circuit even though the flashed lamp may be shorted. Such switch circuits are customarily employed for flashing individual flash lamps, and the four flash lamps of a flashcube.

Electronic firing circuits, employing transistor devices, have been developed for sequentially flashing, one at a time, a plurality of flash lamps in the form of a multiple-flash array. All of the lamps at the front side of the array are flashed without moving or turning the array. An example of such a multiple-flash array, having five flash lamps on each side, is described in US. Pat. Nos. 3,598,984 to Stanley Slomski and 3,598,985 to John Harnden and William Kornrumpf. An example of an electronic firing circuit for a multiple-flash lamp array is described in US. Pat. No. 3,676,045 to Donald Watrous and Paul Cote. The circuit functions, basically, by sequencing past open-circuit flashed lamps,

- and applies a firing pulse to the first lamp in the array having a proper filament resistance (of low value such as 0.6 ohms). An open-circuit flashed lamp, by comparison, normally has a resistance, between its lead-in wires, of a few hundred ohms or greater. If a lamp, upon being flashed, becomes a shorted lamp (as described above having a low resistance of, for example, several ohms or less, the circuit will thereafter apply each succeeding firing pulse to the shorted flashed lamp, and no further good lamps connected in the circuit can be flashed. Thus, the need is evident for a flash lamp design that will almost invariably provide an open circuit'upon flashing.

SUMMARY OF THE INVENTION Objects of the invention are to provide improved photoflash lamps, and to provide photoflash lamps which will almost invariably provide an open circuit upon flashing.

The invention comprises, briefly and in a preferred embodiment, a photoflash lamp of the type having a pair of lead wires extending into a bulb containing combustible metal and a combustion-supporting gas, there being a filament or other flash ignition means connected across the inlead wires within the bulb. In accordance with the invention, a sleeve such as glass, or other electrical and thermal insulation means, is provided around one of the inleads near the filament so that the second inlead is more exposed to heat of combustion of the flashing lamp, for a greater distance from the filament or other ignition means than is the sleeved inlead. When the lamp is flashed. the unsleeved inlead burns back farther than the sleeved inlead, thus causing a relatively large electrical path between exposed parts of the burned-back inleads and reducing the likelihood of them becoming shorted either by direct contact or by metal fragments in the flashed lamp. The insulating means of the invention performs several functions: it causes unequal burn-back of the inleads during lamp flashing, and thereafter functions as an electrical insulator between the burned-back inleads to cause a large separation between the exposed ends thereof, and it prevents direct shorting of the burned-back inleads with one another.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a photoflash lamp in accordance with a preferred embodiment of the invention;

FIG. 2 is a perspective view of the filament mount of the lamp of FIG. I before the lamp is flashed;

FIG. 3 is a perspective view of the mount of FIG. 2, showing its condition after the lamp has been flashed: and

FIG. 4 shows a prior artfilament mount arrangement, viewed the same as in FIGS. 2 and 3, after the lamp has been flashed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The lamp shown in FIG. 1 of the drawing is generally the same as that shown in FIG. 5 of US. Pat. No. 3,506,385 to Kurt Weber and George Cressman, and comprises a tubular envelope 11, preferably made of a borosilicate glass or other suitable vitreous material having a stem press seal 12 at one end thereof through which a pair of lead wires 13,14 extend from the exterior to the interior of the bulb 11 in a mutually parallel spaced apart manner. A bead 16 of glass or other suitable vitreous material secures the inlead portions 17 and 18 of the leads l3 and 14 in spaced relationship to each other within the bulb 11, and a filament l9 coated with suitable primer ignition material is held near the ends thereof by the ends 21 and 22 of the inleads l7 and 18 at a distance above the bead 16. Alternatively, primer material may be applied over the inlead ends 21 and 22, instead of or in addition to being coated on the filament 19.

The bulb 11 is substantially filled with a loose mass of filamentary or shredded metal wire or foil 23, of zirconium or hafnium or other suitable combustible metal. Air is exhausted from the bulb 11, and the bulb is filled with oxygen at a pressure of at least several atmospheres, such as about 5 to 10 atmospheres, and the bulb is sealed off at an exhaust tip 24 at the other end thereof from the stem press seal 12. The lamp may be coated with the usual lacquer or plastic protective coatmg.

In accordance with the invention, one of the inleads I7 is provided with electrical and thermal insulating means 26 extending from the bead 16 to near the end 21 to which the filament 19 is attached. Preferably, the

means 26 is a sleeve of glass or other vitreous material surrounding the inlead 17 in the position shown, and the bottom end of the sleeve 26 preferably is attached to the bead 16 such as by heat-seal bonding, or by seating the lower end of the sleeve 26 in a recess in the bead 16. Alternatively, the sleeve 26 may rest on the top surface of the bead l6, and held in place by the surrounding and engulfing mass of combustible material 23. However, in this latter arrangement, there is some danger of filament 19 becoming damaged by rough handling of the lamp which may cause the sleeve 26 to jostle the combustible metal mass 23 which, in turn, may jostle the filament 19 and break it. The insulating member 26, instead of being a glass sleeve as just described, may be in the form of glass or other insulating material applied onto and around the inlead 17 in the position shown in the drawing. In a lamp construction not having a bead 16, the insulating member 26 may extend downwardly and against or sealed to the bottom 27 of the inner bulb surface adjacent to the inlead 17, as indicated at numeral 27. Alternatively, of course, the insulating member 26 may be provided on the'other inlead 18 instead of on 17 as shown. Also, members 26 of differing lengths or configurations can be provided on both inleads l7 and 18 in accordance with the principles of the invention.

FIG. 2 clearly illustrates the relationship of the insulating member 26 with respect to the glass bead 16, inleads 17 and 18, and filament 19, before the lamp is flashed. FIG. 3 illustrates how, upon the lamp being flashed, the filament 19 has been consumed, the upper end of the inlead 17 has been burned back to a point at or near the top of the insulator 26, as indicated by numeral 28, and the other (uninsulated) inlead 18 has burned back to a point at or near the top of bead 16, as indicated by numeral 29, usually in the form of a globule. Thus, the exposed burned-back ends 28 and 29 of the inleads are asymmetrically (vertically) offset from each other and are considerably farther apart from each other, for example three-sixteenths of an inch or more in a typical FlashBar array type of flash lamp, than would be the spacing between them, of about one-sixteenths of an inch or less in the same lamp without the insulating member 26, thus providing a longer electrical path between them and reducing the likelihood of a shorted lamp. As is illustrated by FlG.

, 4, the burned-back ends 28 and 29 of the inleads 17,18

of a prior art lamp will both be burned back approximately the same amount, and with great likelihood that in some of the lamps the burned-back ends 28 and 29 will form globules or perhaps a single combined globule, or will be bent and distorted towards each other due to the heat of combustion when the lamp flashed, thus tending to short circuit either directly against one another or making it all the more likely that unburned metal fragments in the flashed lamp can bridge the gap therebetween and cause a short. By contrast, a flashed lamp of the type in accordance with the invention, as shown in FIG. 3, virtually assures that there cannot be any direct electrical contacting short between the burned-back inleads, and, due to the greater spacing and longer electrical path between the exposed ends 28 and 29 of the burned-back inleads, there is much less likelihood of unburned metal fragments in the lamp making a shorting contact between them. Also, it is found that the longitudinal (vertical) offset spacing between the burned-back ends 28 and 29 of the inleads helps to prevent unburned metal fragments from forming a shorting path therebetween. The size and material of the sleeve 26 must be such that it will withstand the heat of combustion when the lamp flashes.

In the construction shown in FIG. 1, the diameter of the support bead 16 is sufficiently large with respect to the inner diameter of the bulb 11, and is sufficiently near the bottom stem press portion 12 of the bulb, that there is very little likelihood of any uncomsumed metal fragments in a flashed lamp falling around and below the bead 16 and making a shorting contact between the inleads 17 and 18 beneath the bead 16.

It has been found that the invention achieves the objective of providing a flash lamp construction which will almost invariably provide an open circuit upon flashing, rather than a short circuit. For example, in regular commercial production of several million flash lamps made in accordance with the invention, comprehensive testing has shown that the likelihood of shorted lamps occurring upon flashing is only about one lamp out of morethan ten thousand lamps flashed.

The invention can be useful in preventing the inleads from directly shorting in flash lamps not containing metal combustible material. Also, the objectives of the invention can be met, at least in part, by a semicylinder or other shape of the electrical insulating means 26 arranged between the inleads and along the adjacent to or against one of the inleads.

While preferred embodiments of the invention have been shown and described, various other embodiments and modifications thereof will become apparent to persons skilled in the art and will fall within the scope of the invention as defined in the following claims. The terminology in the claims concerning electrical insulation on one inlead includes the possibility of also providing electrical insulation on the other inlead of a size or configuration to achieve the non-symmetrical inlead burn-back effect and result of the invention.

What we claim as new and desire to secure by letters patent of the United States is:

1. A photoflash lamp of the type having a bulb, a pair of inleads extending inside said bulb in substantially mutually parallel spaced apart relationship with each other, and flash ignition means connected between said inleads within said bulb, said bulb containing combustible material ignitable by said flash ignition means, wherein the improvement comprises insulating means arranged between said inleads and along and adjacent to at least part of the length of one of said inleads so that, upon flashing of the lamp and burning back of the inleads, there will be a longer electrical path between the burned-back inleads than would be the case with out said insulating means.

2. A lamp as claimed in claim 1 in which said combustible material comprises a loose mass of metal in filamentary form, and in which said bulb contains a combustion-supporting gas. I

3. A lamp as claimed in claim 1 inwhich said flash ignition means is positioned substantially laterally across said inleads, and in which said insulating means comprises a sleeve positioned around and along a portion of said one inlead.

4. A lamp as claimed in claim 3 including inlead support means of vitreous material surrounding and holding said inleads at a position spaced from said flash ignition means, said sleeve on said one inlead extending from the surface of said inlead support means to a point near said flash ignition means.

5. A lamp as claimed in claim 4 including means for holding said sleeve by said inlead support means.

6. A lamp as claimed in claim 5 in which said sleeve is bonded to said inlead support means.

7. A lamp as claimed in claim 6 in which said inlead support means comprises a bead positioned within said bulb.

8. A photoflash lamp of the type having a bulb, a pair of inleads extending inside said bulb in substantially mutually parallel spaced apart relationship with each other, and flash ignition means connected across said inleads within said bulb, said bulb containing a loose mass of filamentary combustible metal and a combustion-supporting gas, wherein the improvement comprises a sleeve of insulating material positioned around and along at least a portion of the length of a first one of said inleads between its point of entry into the bulb and said flash ignition means so that the second inlead is more greatly exposed to the heat of flash combustion for a greater distance from said flash ignition means than is said first inlead, so that when the lamp is flashed said second inlead burns back farther than does said first inlead, thereby causing an offset, relatively long electrical path between the exposed parts of the burned-back inleads thus reducing the likelihood of a conductive path occurring thereacross.

9. A lamp as claimed in claim 8 in which said flash ignition means is positioned substantially laterally across said inleads.

10. A lamp as claimed in claim 9 including a bead of vitreous material positioned within said bulb and surrounding and holding said inleads at a position spaced from said flash ignition means, said sleeve extending from the surface of said bead to a point near said flash ignition means.

11. A lamp as claimed in claim 10 including means for holding said sleeve by said bead.

12. A lamp as claimed in claim 11 in which said sleeve is bonded to said bead. 

1. A photoflash lamp of the type having a bulb, a pair of inleads extending inside said bulb in substantially mutually parallel spaced apart relationship with each other, and flash ignition means connected between said inleads within said bulb, said bulb containing combustible material ignitable by said flash ignition means, wherein the improvement comprises insulating means arranged between said inleads and along and adjacent to at least part of the length of one of said inleads so that, upon flashing of the lamp and burning back of the inleads, there will be a longer electrical path between the burned-back inleads than would be the case without said insulating means.
 2. A lamp as claimed in claim 1 in which said combustible material comprises a loose mass of metal in filamentary form, and in which said bulb contains a combustion-supporting gas.
 3. A lamp as claimed in claim 1 in which said flash ignition means is positioned substantially laterally across said inleads, and in which said insulating means comprises a sleeve positioned around and along a portion of said one inlead.
 4. A lamp as claimed in claim 3 including inlead support means of vitreous material surrounding and holding said inleads at a position spaced from said flash ignition means, said sleeve on said one inlead extending from the surface of said inlead support means to a point near said flash ignition means.
 5. A lamp as claimed in claim 4 including means for holding said sleeve by said inlead support means.
 6. A lamp as claimed in claim 5 in which said sleeve is bonded to said inlead support means.
 7. A lamp as claimed in claim 6 in which said inlead support means comprises a bead positioned within said bulb.
 8. A photoflash lamp of the type having a bulb, a pair of inleads extending inside said bulb in substantially mutually parallel spaced apart relationship with each other, and flash ignition means connected across said inleads within said bulb, said bulb containing a loose mass of filamentary combustible metal and a combustion-supporting gas, wherein the improvement comprises a sleeve of insulating material positioned around and along at least a portion of the length of a first one of said inleads between its point of entry into the bulb and said flash ignition means so that the second inlead is more greatly exposed to the heat of flash combustion for a greater distance from said flash ignition means than is said first inlead, so that when the lamp is flashed said second inlead burns back farther than does said first inlead, thereby causing an offset, relatively long electrical path between the exposed parts of the burned-back inleads thus reducing the likelihood of a conductive path occurring thereacRoss.
 9. A lamp as claimed in claim 8 in which said flash ignition means is positioned substantially laterally across said inleads.
 10. A lamp as claimed in claim 9 including a bead of vitreous material positioned within said bulb and surrounding and holding said inleads at a position spaced from said flash ignition means, said sleeve extending from the surface of said bead to a point near said flash ignition means.
 11. A lamp as claimed in claim 10 including means for holding said sleeve by said bead.
 12. A lamp as claimed in claim 11 in which said sleeve is bonded to said bead. 